The present invention relates to a multiple reader/printer developer apparatus and particlarly to such apparatus to display the image of a film and selectively copy said image.
The recent development of film storage systems has resulted in a demand for combined printer/reader to retrieve the information in the storage film. Various systems have been developed. A particularly satisfactory dry silver paper developer and process is disclosed in U.S. Pat. No. 4,322,158 which issued Sept. 8, 1981. The above patent discloses a reader/printer apparatus having means for introducing a storage film negative on which the information is carried. An optical system provides for projection of an enlarged image onto a display screen. The apparatus further includes a printing unit which permits printing of the displayed information. The printing unit includes a thermal developer having a uniquely heated roller and heating bar for guiding and developing the imaged copy paper through the developer. Other types of developing systems are used and available in the art. For example, electrostatic developers have been used in which a photoconductive copy paper is exposed to form a latent image from a positive or negative carrier and then developed. Various systems have been suggested, such as shown in U.S. Pat. Nos. 4,166,691 issued Sept. 4, 1979, 4,155,330 issued May 22, 1979, and 4,288,519 issued Sept. 8, 1981. A direct reversal development apparatus is also disclosed in the copending application of Ronald Frias entitled "Single Step Reversal Electrostatic Developing Method and Apparatus" which was filed on even date herewith and which is assigned to a common assignee herewith. The latter application discloses a means for exposing the negative image on an appropriately photoconductive coated paper and passing the exposed paper through a magnetic toner brush developer for directly depositing of the toner particles directly onto the exposed neutral areas of the exposed paper. This of course provides a single step direct reversal development of the negative. The various users may of course prefer one developer or the other. The electrostatic process for example is somewhat less costly when compared to the dry silver paper process. A high volume user may therefore prefer to use the electrostatic process. However, the electrostatic developer requires the use of a toner, and the addition and removal of the toner particles supply. The machine is also subject to the possibility of the toner particles entering the mechanism. The user may therefore prefer a dry silver process wherein the total development chemistry is incorporated directly into the copy paper and development only requires appropriate heating of the paper to generate the image and form the hard copy.
Generally, completely separate reader/printer apparatus have been developed and marketed for each type of development process.
In the toner system developing process, the photocopy paper includes a photoconductive layer which is charged generally through a corona charging apparatus, to a high electrical charge level which may be either a positive charge or a negative charge. Such high voltage structure is not required in the dry silver process. The charged copy paper in the electrostatic process is then passed through an optical system and exposed to the positive or negative image. During the exposure, the transmitted light, which defines the image, effectively neutralizes the charge in the photoconductive layer, resulting in creation of the latent image in the charged layer.
The corona charging device is a high voltage device and the characteristic of the print is of course directly related to the effectiveness of the charging. Further, the corona charging device generally uses a thin, delicate wire for appropriate charging. This may require replacement and and of course a simple, construction is desired to permit reliable and convenient servicing by the user or service personnel.
The devices are generally distinctly constructed for the particular development process and various acceptable reader/printers are available. Such production of completely separate systems necessarily results in a high inventory cost as well increase in the cost of the machines.
There is a need for a reader/printer apparatus which can be readily constructed with either one of a number of different types of developing apparatus having a common basic main frame and particularly such apparatus which permits construction as a magnetic toner brush developer with a corona charging unit or a dry silver thermal paper developer without significant and expensive modification to the basic main frame.